Transformer coils with insulating spacer



' Dec. 8, 1970 F. w. HEINRICHS, JR, ETAL 3,546,646

TRANSFORMER COILS WITH INSULATING SPACER Filed Feb. .19, 1969 2 Sheets-Sheet 1 IIIM II.

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United States Patent 3,546,646 TRANSFORMER COILS WITH INSULATING SPACER Frank W. Heinrichs, Jr., McMurray, Lawrence R. Toothman, and Charles C. Honey, Pittsburgh, and Anthony J. .lonnatti, Glenshaw, Pa., assignors to McGraw-Edison Company, Elgin, Ill., a corporation of Delaware Filed Feb. 19, 1969, Ser. No. 800,474 Int. Cl. H01j 27/10 U.S. Cl. 336-60 12 Claims ABSTRACT OF THE DISCLOSURE This invention relates to an electrically insulating spacer strip for maintaining spacings between electrical windings and between insulating parts between windings and to a method of making such a spacer strip.

The coils of transformer windings and in particular, coils of high voltage power transformer windings, are frequently spaced apart as a means of electrically insulating the coils and to provide space for circulation of cooling fluid between the coils. A common and well known means of maintaining the coils spaced apart is to position numerous individual spacer blocks between adjacent coils. This arrangement also commonly includes the positioning of a pressboard washer between the coils on which the spacer blocks are glued. There are several disadvantages of using such spacer blocks and these include the relatively expensive individual fabrication and positioning of each block on the washer. Further, each spacer must be individually glued on the washer so that each of a large number of glue joints provides a potential source for trapped air bubbles and accompanying corona problems.

It is an object of the present invention to provide a spacer strip including a plurality of spacer blocks for spacing apart electrical coils and insulating parts of a transformer winding.

It is another object of the invention to provide a single piece spacer strip including a plurality of spacer blocks for spacing part electrical coils of a transformer winding and an economical method of manufacture therefore.

It is a further object of the invention to provide a continuous spacer strip having a plurality of spacer blocks formed therein at spaced apart intervals and an economical method of manufacture therefore.

It is a further object of the invention to provide a single piece spacer strip having a plurality of spaced apart spacer blocks formed from folds of said strip and an economical method of manufacture therefore.

It is a still further object of the invention to provide a single piece spacer strip having a plurality of spacer blocks spaced apart along the length of the strip and a plurality of narrow strip widths between adjacent spacer blocks and being spirally wound between adjacent coils 3,546,646 Patented Dec. 8, 1970 of an electrical transformer winding with edges facing and spacer blocks of each strip turn being inserted into narrow widths of adjacent strip turns.

The objects of the invention are accomplished by providing a spacer strip comprising a continuous length of insulating strip material having at least one fold formed therein at spaced apart intervals. Each fold location forms a spacer in the strip and the desired thickness of the spacer determines the number of folds taken at a location and stacked substantially parallel with the strip. The folds are held against the strip or each other by a suitable fastening means such as an insulative adhesive. Strip lengths between adjacent spacers are narrow and the spacer strip is positioned between coil windings in a spiral arrangement with edges facing and spacers inserted into narrow lengths of adjacent strip turns to form an interlocked structure for holding the coil windings apart. One or more pleats in narrow lengths where the strip is bent permit its bending in planes parallel to the wide surface of the strip. The method of fabricating the spacer strip comprises the steps of forming at least one loop in a continuous strip of insulating material at spaced apart locations along the length of the strip. A fastening means such as an insulating glue is applied to the loop and/or strip prior to folding and the loop is then folded over substantially parallel to the strip and held in place by the glue. Additional steps include the forming of the narrow strip widths between spacers and forming pleats at thenarrow width locations.

Other objects and advantages of the invention will in part be obvious and will in part appear hereinafter. For a fuller understanding of the nature and objects of the invention, reference should be had to the following detailed description taken in connection with the accompanying drawings in which:

FIG. 1 is a plan view of a portion of the spacer strip of the invention;

FIG. 2 is a side elevation of a portion of the spacer strip of the invention;

FIG. 3 is a side elevation showing strip loops forming spacers before and subsequent to folding;

FIG. 4 is a side elevation of an alternate embodiment of the invention showing a loop forming a spacer before and subsequent to folding;

FIG. 5 is a plan view showing the spacer strip of the invention spirally wound parallel to a transformer pancake coil;

FIG. 6 is an end elevation of the transformer coils and spacer strip shown in FIG. 5;

FIG. 7 is a block diagram showing the method of the invention; and

FIG. 8 is a side elevation, partly in cross section, showing loop forming and folding means for fabricating a spacer block in a length of strip material.

With reference to the drawings, a continuous spacer strip 2 of an insulating material such as paper is shown. A paper such as cylinder paper which is well known in the art and has a specific gravity of up to 1.3 is suitable. The spacer strip 2 comprises a plurality of narrow areas 4 and a plurality of thickened areas or spacers 6 spaced apart along the length of the strip 2. Each thickened area 6 includes a length 8 of the strip 2 folded parallel to the strip 2. As shown in FIGS. 2 and 3, each spacer 6 may include one or more displaced portions or loops 10 which, when folded, are stacked parallel with the strip 2 to provide the spacers 6 With a thickness comprising the multiple thicknesses of the strip 2. The spacers 6 are held folded by glue between adjacent portions of the loops 10 and between the strip 2 and the loops 10. Each loop has an end 12 which is not displaced with the rest of its length and which remains substantially aligned with the length of strip 2. Where the spacer 6 is formed from a plurality of loops or displaced portions 10, an end 12 of each loop 10 adjoins an end 12 of an adjacent loop 10.

As best seen in FIG. 5, the narrow areas 4 comprise lengths in the strip 2 which have decreased strip widths for a distance along the length of the strip at least equal to the length along the strip of a thickened area 6. Each spacer or thickened area 6 extends into an adjacent narrow area 4 when the strip 2 is spirally wound with edges facing, as shown in FIG. 5. When the strip is spirally wound on the transformer pancake winding 20, the narrow areas 4 are shown in FIG. 1 as having generally curved edges although any other edge shape which will accommodate the interfitted spacers 6 is also suitable. Each narrow area 4 may have one or more transverse pleats 14 formed in its length intermediate the thickened areas 6. Similar to the loops 10, the pleats 14 are displaced portions of the strip 2. The function of the pleats 14 is to allow bending of the strip 2 in a direction parallel to its width and flat surface 16.

Another embodiment of the spacer strip 2 is shown in FIG. 4 and has elements similar to those shown in FIGS. 1 and 2 identified by the same number with the addition of a prime mark. In FIG. 4, a loop or displaced portion 10 is formed in a length 8' of the spacer strip 2' and folded over to form the spacer 18. An additional length of insulating strip material 17 is positioned in engagement with strip 2 prior to folding and, upon folding, the spacer 18 has an overall thickness comprising the thickness of the strip 2', the folded thicknesses of the loop 10 and at least one thickness of the additional strip 17. The additional strip 17 may be of a short length which engages the nondisplaced portion of strip 2' or engages all or a part of loop 10, as shown in FIG. 4. The strip 17 may also be of a continuous length coextensive with strip 2'.

The entire spacer strip 2 is spirally wound and fastened on the washer 22 with its edges 3 and 5 facing each other and the thickened areas 6 inserted into the narrow areas 4 to form an interlocked continuous spacer. As shown in FIG. 6, the spacer strip 2 with its thickened areas 6 maintains the pancake coils spaced apart a distance determined by the overall thickness of the thickened areas 6 and the density of the insulation material used in forming the thickened areas 6. The arrangement of the thickened areas 6 shown in FIG. 6 also permits circulation of cooling fluid between the coils 20 to aid in cooling of the transformer winding.

The method of making the spacer strip 2 generally includes the steps of cutting narrow areas 4 in a continuous strip of insulating material 1, forming loops 10 in the strip 1, forming pleats 14 in the strip 1 and moving the loops 10 together and folding them over toward the strip 1. The method may also include the additional steps of applying a pressure or water activated glue or adhesive such as polyvinyl alcohol to the strip 1 adjacent the fold locations and activating the glue just prior to the folding steps.

A block diagram illustrating apparatus for performing the steps of the invention is shown in FIG. 7. A drive means (not shown) may be utilized for running the strip material 1 off of the roll and advancing the strip 1 through or past the various stations of the apparatus. The drive means may be of any type well known in the art and therefore is not shown in the drawings and will not be discussed herein. The strip 1 is continuously advanced through a cutting means 32 where the spaced apart narrow areas 4 are cut in the strip 1 and past a glue applying means 34 where a water sensitive adhesive is applied to predetermined lengths 8 in which the loops 1!) are to be formed. The cutting means 32 and the glue applying means 34 are both of a type well known in the art and will not be described in detail. The strip 1 is then advanced into the loop forming means 36 and the pleat forming means 38 where the loops 10 and pleats 14 are respectively formed. After forming of the loops 10, the activating means 42 sprays water against the adhesive to activate it and the thickened areas or spacers 6 are then formed in the strip 1 by the folding means which folds the loops 10 toward and parallel with the strip 1. Repeating of the foregoing operations in the strip 1 results in the spacer strip 2 having the spaced apart thickened areas 6 and the narrow areas 4 with pleats 14 formed therein between the thickened areas 6. It should be understood that the order of the steps may vary somewhat with the order shown in FIG. 7. However, it is required that the loops 10 be made in the strip 1 and glue applied to the loops before the loops 10 are folded over.

The continuous strip 1 is typically available in rolled form for advancing between the spray nozzles 44 and 46 of the glue applying means 34. The nozzles 44 and 46 spray the adhesive on the strip 1 where the loops 10 are to be folded and on to the lengths 8 in which the loops 10 are to be formed. The lengths 8 are then advanced to the loop forming means 36 with the narrow areas 4 immediately preceding the lengths 8 being positioned in the pleat forming means 38. The pleat forming means 38 includes an upper die member 48 and a lower die member 50 which are brought together by a drive means (not shown) from the spaced apart position shown in phantom view to the closed position shown in full lines in FIG. 8 when a narrow area 4 is between the die members 48 and 50. The upper die member 48 has an alternating series of projections and cavities 52 and 54, respectively, and the lower die member 50- has an alternating series of cavities and projections 56 and 58, respectively, which mate with the projections and cavities 5'2 and 54 when the die members 48 and 50 are brought together. The projections and cavities of the die members 48 and 50 are enlarged somewhat beyond actual size in FIG. 8 for the purpose of clarity. When the die members 48 and 50 are brought together, the cavities and projections 56 and 52 and 54 and 58 will displace a portion of the strip 1 to form the pleats 14 and as the die members 48 and 50 come more tightly together, the flat surfaces 60 and 62 of the die members 48 and 50 and the cavities and projections will clamp the strip 1 so that it may not move back towards the loop forming means 36.

The loop forming means has an upper die 64 provided with one or more loop forming cavities 66 and a lower die 68 having one or more fingers 70 which correspond to each of the cavities 66. Just after the die members 48 and 50 clamp the strip 1 in place the die members 64 and 6% moved together by a drive means (not shown) from the phantom position to the full line position shown in FIG. 8 so that the finger 70' displaces the lengths 8 in strip 1 transversely of the strip 1 and in a manner moving the ends 12 of a loop 10 closer together. As the dies 64' and 68 move together, the finger 70 extends fully into the cavities 66 to form the loop 10 in the length 8 of strip 1. The ends 12 of the loops or displaced portions 10 are prevented from being displaced relative to the displaced portions 10 by the fiat surfaces 72 and 74, respectively, of upper and lower dies 64 and 68. A plurality of loops 10 such as shown in FIG. 3 may be formed by means 36 by merely adding more cavities 66 and corresponding fingers 70. After the loops 10 have been for-med, the dies of both the loop forming means 36 and pleat forming means 48 move apart to allow advancing of the loops 10 to the folding means 40.

If a water activated adhesive is used to hold the loops 10 in place, then prior to folding of the loop 10 the nozzles 76 and 78 of the glue activating means 42 spray water on the portions of the loops 10 and strip 1 to which glue has previously been applied. The opposite ends 12 of the loops are then moved toward each other and the loop 10 is folded over against the strip 1 by the upsetting arm 80 and toward the table 82 of the folding means 40. While a folding operation is being performed in a length 8 by the folding means 40, another length 8 of the strip 1 may have a loop 10 formed in it by the loop forming means 36. Similarly, pleats 14 may be formed in the strip 1 between the length 8 in which a fold is being made and the length 8 in which another loop 10' is being formed. The foregoing steps may be continuously repeated to form the spacer strip 2 as shown in FIG. 5.

The alternate embodiment shown in FIG. 4 may be made by placing an additional strip 17 on the spacer strip 2' prior to forming of the loop 10'. The strip 17 may be held in place on the strip 2' by any suitbale means such as gluing. The additional strip 17 may be placed in engagement only with the length '8 in which the loop 10" will be formed or the strip 17 may extend along the side of strip 2' toward which the loop 10 is to be folded, depending on the additional thickness to be obtained from the strip 17. If the strip 17 is placed on the strip 2' prior to forming of the loop 10', then the forming operation will result in the forming of a loop in both the length 8 and the strip 17 and the strip 17 and length 8' may be folded together to form the spacer 18. As may be seen in FIG. 4, the spacer 18 has a thickness comprising the thickness of the strip 2', the folded thicknesses of the loop 10' and the folded thicknesses of the additional strip 17.

With reference to FIG. 5, the entire spacer strip 2 may be spirally wound and glued at intermittent points along the length of spacer strip 2 on the washer 22. The spacer strip 2 is wound with its edges 3 and 5 facing each other with the spacers 6 in one turn fitted into the narrow areas 4 of an adjacent turn to produce an interlocked spacer arrangement. The washer 22 is positioned against the pancake coil 20 and another pancake coil 20 is positioned parallel to the washer against the spacers *6 as shown in FIG. 6. The interlocked arrangement of the spacers 6 provide a minimum unsupported span of each winding coil 20' while at the same time permitting coolant circulation between the coils 20. The use of an insulating material such as cylinder paper having a specific gravity of up to 1.3 results in a high spacer compressive strength and also results in a high resilience which allows the spacers 2 to withstand high mechanical shock. Further, because the spacer strip 2 is continuous it need not be glued to the washer 22 at each spacer location. Thus, the number of glue applications having trapped air bubbles are reduced to thereby reduce the number of potential corona sources. A major advantage of the method of the invention is that a continuous spacer strip including all necessary coil spacers can be economically and continuously fabricated. As previously pointed out, a common present method is to individually fabricate each of a high number of spacers required between each adjacent pancake coil.

While two specific embodiments of the article and method of the invention have been shown herein, it will be realized that many modifications thereof are feasible without departing from the spirit and scope of the invention. It is consequently intended in the appended claims to cover all such variations and modifications as fall within the true spirit and scope of the invention.

What is claimed is:

1. In combination with a transformer winding having a plurality of spaced apart stacked coil layers, a spacer positioned between two of said coil layers and comprisng:

a strip of insulating material having a plurality of thickened areas spaced apart along its length; each of said thickened areas comprising a portion of the length of the strip folded against itself; and

each thickened area has a thickness positioned transversely between said two coil layers and holding the coil layers spaced apart.

2. The combination according to claim 1 wherein one of said thickened areas includes a plurality of stacked folds in said length portion.

3. The combination according to claim 1 wherein said strip of insulating material is creased transversely of its length between two adjacent thickened areas whereby said strip may be bent in a plane parallel to its flat surface.

4. A spacer positioned between two stacked pancake coil layers of a transformer Winding and comprising:

a strip of insulating material having opposing ends and a plurality of thick areas spaced apart intermediate said ends and engaging one of said coil layers whereby said coil layers are maintained spaced apart; and

each of said thick areas comprises a fold in said strip positioned between said coil layers and holding the coil layers apart.

5. The combination according to claim 4 wherein said strip has a plurality of flat sides between the thickened areas facing a pancake coil; and each thick area includes a plurality of stacked folds in said strip.

6. The combination according to claim 5 wherein said strip has a plurality of flat sides between the thickened areas facing a pancake coil; and at least one of said flat sides has a crease formed therein and said flat side is bent at said crease in a direction parallel to said pancake coils.

7. The combination according to claim 6 wherein said strip of insulating material comprises insulating paper.

8. The combination according to claim 1 wherein:

said strip of insulating material has two opposing ends;

and

said plurality of thickened areas are positioned intermediate said ends.

9. The combination according to claim 1 wherein each two of said thickened areas define an open space along said strip.

10. In combination with a transformer winding having a plurality of spaced apart coils, a spacer positioned between two of said coils and comprising:

a first strip of insulating material having a plurality of thickened areas spaced apart along its length;

a plurality of second strips of insulating material shorter than said first strip and spaced apart along the length of the first strip at said thickened areas;

each of said thickened areas comprising a folded portion of the length of the first strip and one of said second strips folded between said length portion; and

each thickened area has a thickness positioned transversely between said two coils whereby the coils are maintained spaced apart.

'11. In combination with a transformer winding having a plurality of spaced apart coils, a spacer positioned between two of said coils and comprising:

a strip of insulating material having a plurality of thickened areas spaced apart along its length and having two edge surfaces defining a width, said width being wider at the thickened areas than between the thickened areas, said thickened areas each having opposing ends positioned at said edge surfaces;

each of said thickened areas having a thickness comprising a portion of the length of the strip folded against itself; and

said strip has a spirally wound position between said coils to form a plurality of strip turns having said edge surfaces facing each other and the ends of the thickened areas of adjacent strip turns interfitting, the thickness of each thickened area being positioned transversely between said coils whereby the coils are maintained spaced apart.

12. A spacer positioned between two pancake coils of a transformer winding and comprising:

a strip of insulating material having a plurality of thickened areas each comprising a plurality of stacked folds in said strip, said thickened areas being spaced apart along the length of the strip and engaging one of said coils whereby said coils are maintained spaced References Cited apart; said strip having a plurality of flat sides between the UNITED STATES PATENTS thickened areas facing a pancakeicoil; 1,908,063 5/1933 Schnelder 174 113X said strip having a narrow width portion between ad- 2,924,799 2/1960 Hatfield 336"199X jacent thickened areas and a relatively wider width 5 3,368,174 2/1968 Flschel' 336-199 portion coextensive with said thickened areas; and ELLIOT GOLDBERG Primary Examiner said strip is wound between saidpancake coils with US. Cl. X.R.

said wider width portions inserted into said narrower width portions. 336-499 UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Dated December 8,

Toothman,

Patent No. 3,546,646

Frank W. Heinrichs, Jr. Lawrence R. fl LQhgples C. Honey, Anthony J. Jonnattrl It is certified that error appears in the above-identified patent and that eaicl Letters Petent ere hereby corrected as shown below:

1'" Claim 5, lines 18-20, cancel "said strip has a plurality of flat sides between the thickened areas facing a panca coil; and". g

a I an. 15 Attelt: 

